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Abstract:

A method for producing an artificial bone capable of accurate molding at
a joined part with appropriate strength, in which electromagnetic waves
or electron beams are irradiated to a layer of at least type of powder
selected from metal biomaterials, ceramics for the artificial bone and
plastic resins for the artificial bone based on image data corresponding
to a shape of the artificial bone, thereby effecting sintering or
melting, and the thus sintered layer or melted and solidified layer is
laminated, such that a surface finish step is adopted that inner faces
and/or outer faces of both ends and their vicinities configuring the
joined part to a human bone part are polished by a rotating tool based on
the image data and also irradiation of electromagnetic waves or electron
beams at both ends and their vicinities constituting the joined part is
set greater than that at other regions,

Claims:

1. A method for producing an artificial bone comprising the steps of:
irradiating one of electromagnetic waves and electron beams to a layer of
at least one type of powder selected from metal biomaterials, ceramics
for an artificial bone and plastic resins for an artificial bone, based
on image data corresponding to a shape of the artificial bone, thereby
effecting at least one of sintering and melting, laminating the thus
sintered layer or the thus melted and solidified layer, a surface finish
step of polishing at least one of inner faces and/or outer faces of both
ends and vicinities thereof configuring a joined part to a human bone
part by a rotating tool based on the image data, and said step of
irradiating includes irradiation of said one of electromagnetic waves and
electron beams at both ends and their vicinities configuring the joined
part to be greater than that at other regions.

2. The method for producing an artificial bone according to claim 1,
wherein a maximum diameter of surface roughness based on the polishing by
the rotating tool is 10 μm.

3. The method for producing an artificial bone according to claim 1,
further comprising: a polishing step for polishing leading end faces of
both ends by the rotating tool.

4. The method for producing an artificial bone according to claim 1,
further comprising the step of: forming one of a meshed region and a pore
aggregate region on at least some of a hollow peripheral wall along a
longitudinal direction and the formed region is provided with a greater
irradiation dose of said one of electromagnetic waves and electron beams
than other regions.

5. The method for producing an artificial bone according to claim 1,
further comprising the step of: using a CAD system to set image data
corresponding to a shape of the artificial bone, and using one of a CAD
system and a CAM system to set at least one of the following: irradiation
dose per unit area, and irradiation time of said one of electromagnetic
waves and electron beams in the artificial bone.

6. The method for producing an artificial bone according to claim 5,
further comprising the step of: using the one of the CAD system and the
CAM system to set at least one of the moving velocity and rotating
velocity of the rotating tool in accordance with at least one of:
irradiation dose per unit area, and irradiation time of said one of
electromagnetic waves and electron beams.

7. The method for producing an artificial bone according to claim 1,
further comprising the step of: forming at least some regions inside a
peripheral wall along a longitudinal direction, besides both ends forming
joint parts and positions of neighborhoods thereof, into a three
dimensional meshed state.

8. The method for producing an artificial bone according to claim 1,
further comprising the step of: setting a spot diameter to be irradiated
with said one of electromagnetic waves and electron beams less than 100
μm.

9. The method for producing an artificial bone according to claim 1,
further comprising the step of: adopting, as a laminated powder at both
ends and vicinities thereof configuring the joined part, one of metal
biomaterial powder and powder which is substantially composed of the
metal biomaterial powder.

10. An artificial bone produced by the method for producing an artificial
bone according to claim 1.

Description:

FIELD OF THE INVENTION

[0001] The present invention relates to a method for producing an
artificial bone used in surgery of human bodies and others by utilizing a
three-dimensional shaping method and an artificial bone based on the
method.

DESCRIPTION OF THE RELATED ART

[0002] There is a trend that demand for transplantation of an artificial
bone for a bone part of a human body where a defect or damage has
occurred has increased in line with the development of medical
technology.

[0003] As shown in Patent Document 1, there has been extensively used a
method for producing an artificial bone in which a layer of one or more
types of powder selected from metals, resins and ceramics is subjected to
laser sintering based on artificial bone image data and the sintered
layer is laminated.

[0004] Incidentally, it is an inevability in molding artificial bones that
an artificial bone is molded accurately at both ends and their vicinities
constituting a joined part to a human bone part.

[0005] However, in a conventional method for producing an artificial bone,
no particular attention has been paid or no device has been made in this
respect. And Patent Document 1 is no exception.

[0006] Further, the joined part of an artificial bone is required to be
made stronger than other regions in order to prevent fatigue or friction
resulting from joining.

[0007] However, despite the fact that the above-described laser sintering
has been adopted, conventional techniques have failed to provide a
configuration in which particular attention is paid to this respect.

PRIOR ART DOCUMENTS

Patent Document

[0008][Patent Document 1] WO2007/122783

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

[0009] An object of the present invention is to provide a method for
producing an artificial bone capable of realizing accurate molding at a
joined part with appropriate strength and an artificial bone based on the
method.

Means for Solving the Problems

[0010] In order to attain the above object, a basic configuration of the
present invention is made up of the following:

[0011] (1) a method for producing an artificial bone in which
electromagnetic waves or electron beams are irradiated to a layer of one
or more types of powder selected from metal biomaterials, ceramics for an
artificial bone and plastic resins for an artificial bone based on image
data corresponding to a shape of the artificial bone, thereby effecting
sintering or melting, and the thus sintered layer or the thus melted and
solidified layer is laminated, and the method for producing an artificial
bone in which a surface finish step is adopted in which inner faces
and/or outer faces of both ends and their vicinities configuring a joined
part to a human bone part are polished by a rotating tool based on the
image data, and irradiation of electromagnetic waves or electron beams at
both ends and their vicinities configuring the joined part is made
greater than that at other regions,

[0012] (2) an artificial bone which is produced by any one of the
above-described methods of (1).

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 show an artificial bone which is hollow inside. FIG. 1 (a)
is a sketch showing a pipe-shaped artificial bone, FIG. 1 (b) is a sketch
showing a partially pipe-shaped artificial bone, and FIG. (c) is a sketch
showing a combination of the pipe shaped artificial bone with the
partially pipe-shaped artificial bone.

[0014] FIG. 2 show an artificial bone in which the interior of a
peripheral wall along the longitudinal direction is in a
three-dimensional meshed state. FIG. 2 (a) is a cross-sectional view
taken in the longitudinal direction, FIG. 2 (b) is a cross-sectional view
taken in a direction orthogonal to the longitudinal direction (the cross
section shown in. 2 (b) shows a portion taken along the line A to A in
FIG. 2 (a)).

[0015] FIG. 3 show an artificial bone which forms a hollow peripheral wall
along the longitudinal direction. FIG. 3 (a) is a side elevational view
where the peripheral wall is in a meshed state, and FIG. 3 (b) is a side
elevational view where the peripheral wall is in a pore aggregate state.

[0016] FIG. 4 explain that powder is subjected to irradiation by
electromagnetic waves or electron beams and polished by a rotating tool,
thereby molding an artificial bone. FIG. 4 (a) is a cross-sectional view
showing a sintering step in which electromagnetic waves or electron beams
are irradiated, FIG. 4 (b) is a cross-sectional view showing a polishing
step in which an outer wall of the sintered region is molded, FIG. 4 (c)
is a cross-sectional view showing a laminating step in which powder is
additionally laminated after completion of the polishing step to mold the
outer wall, and FIG. 4 (d) is a cross-sectional view showing a step in
which the inner wall is molded after completion of steps (a), (b) and (c)
(the white arrows indicate a state that a rotating tool rotates around
and the solid arrows indicate a state that the rotating tool rotates on
its own axis).

[0017]FIG. 5 is a block diagram showing a case where a CAD/CAM system is
applied to the present invention.

[0029] In general, an artificial bone 1 adopts any one of a configuration
in which a peripheral wall is made hollow inside as shown in FIG. 1 and a
configuration in which the peripheral wall is in a meshed state of a
three-dimensional structure inside as shown in FIG. 2. (In FIG. 2, the
meshed state of the three-dimensional structure is provided all over a
region along the longitudinal direction, but a configuration may also be
adopted in which a meshed state is provided at a partial region such as
both ends and the inside of the peripheral wall besides both ends forming
a joined part and positions of their neighborhoods.)

[0030] However, the above-described hollow artificial bone includes any
one of the pipe shape, the partial pipe shape and the combination of them
as shown in FIGS. 1(a), (b) and (c). Further, for the purpose of
infiltration of body fluid or allowing body fluid to enter into human
tissue, as shown in FIGS. 3(a) and (b), there may be adopted an
artificial bone in which a meshed state or a pore aggregate state is
provided at all or some regions of a peripheral wall along the
longitudinal direction. (In FIGS. 3(a) and (b), there is adopted an
artificial bone in which the meshed state or the pore aggregate state is
provided at regions other than both ends 11 and their vicinities.
However, as a matter of course, it is possible to adopt such a
configuration in which any one of these states also covers the both ends
11 and their vicinities.)

[0031] In any mode, the artificial bone 1 is joined to a human bone at
both ends and their vicinities.

[0032] In most cases, the artificial bone 1 is firmly joined to a human
bone with a screw in such a manner that the artificial bone 1 is placed
outside and the human bone is placed inside. However, as an exception,
they can be joined in such a manner that the human bone is placed outside
and the artificial bone 1 is placed inside.

[0033] Nevertheless, at both ends 11 and their vicinities configuring a
joined part, an artificial bone is required to be molded accurately
according to the shape of a human bone. Further, for the purpose of
avoiding friction and fatigue at the joined part, the joined part is
required to be made greater in strength than other regions.

[0034] In the previously described basic configuration (1), as shown in
FIGS. 4 (a) and (c), based on the conventional techniques in which
electromagnetic waves or electron beams 7 are irradiated to a layer of
one or more types of powder 2 selected from metal biomaterials, ceramics
for the artificial bone 1 and plastic resins for the artificial bone 1 to
effect sintering and these sintered layers are laminated sequentially,
inner faces and/or outer faces of the ends 11 and their vicinities where
joining is performed are polished by a rotating tool 6, thereby
conducting final molding as shown in FIGS. 4 (b) and (d). And, an
accurately joined face is provided by this claim.

[0035] Then, where a maximum diameter of surface roughness based on the
polishing by the rotating tool 6 is to be 10 μm, it is possible to
provide an extremely accurate molding and match the needs of medical
practices.

[0036] There is found no particular trouble resulting from polishing by
the rotating tool 6 on inner faces of the ends 11 and their vicinities
configuring a joined part. Therefore, in this respect, the basic
configuration (1) has technical value.

[0037] In an artificial bone 1 where an inner face other than the ends 11
and their vicinities are bent or in an artificial bone 1 where a part
further inside the ends 11 and their vicinities is increased in diameter,
an ordinary rotating tool 6 smaller in rotating diameter may cause
trouble in polishing and molding an inner face.

[0038] However, even in these cases, for example, a specially shaped
rotating tool having an enlarged rotating diameter at the leading end can
be used to overcome the above trouble.

[0039] The basic configuration (1) also includes a method for polishing
and polishing both inner faces and outer faces of the ends 11 and their
vicinities. In this configuration, it is possible not only to provide
accurate molding on an inner face to be joined but also to mold a smooth
outer face at the end 11 by polishing and polishing, thereby avoiding
unnecessary muscle adhesion.

[0040] With attention given to the above situation, the basic
configuration (1) has adopted a surface finish step in which a region
other than a joined part to a human bone part on an outer face of the
artificial bone 1 may be polished by the rotating tool 6.

[0041] There is such a case that a complicated shape is formed at a
leading end of the joined end 11 to a human bone part.

[0042] In this case, an embodiment having a polishing step in which
leading end faces at both ends are polished by the rotating tool 6
enables accurately shaping the leading end which is complicated in shape,
therefore it is favorably applicable.

[0043] In normal molding, an outer face is polished and molded by the
rotating tool 6 after being sintered by means of electromagnetic waves or
electron beams 7 and molded, then laminated further, while in most cases
an inner face is polished and molded after completion of polishing and
molding of the outer face.

[0044] Where the leading end faces of the both ends 11 configuring the
joined part are polished by the rotating tool 6, these faces may be
polished before or after polishing of the inner face. Inmost cases, these
faces are polished before that.

[0045] In the basic configuration (1), irradiation at the ends 11 and
their vicinities configuring a joined part is made greater than that at
other regions, thereby increasing the strength of the joined part and
decreasing the friction and fatigue of the artificial bone 1 at the
joined part as much as possible.

[0046] To set an irradiation dose at the ends 11 and their vicinities,
either one of which the irradiation dose per unit area is increased or
the irradiation time is prolonged can be selected.

[0047] Where a three-dimensional meshed state or a pore aggregate state is
formed at all or some of a peripheral wall along the longitudinal
direction as shown in FIGS. 3(a) and (b), in order to maintain necessary
strength at a region covering an intermediate portion of the peripheral
wall, irradiation dose of electromagnetic waves or electron beams 7 can
be set greater than other regions free of the above state.

[0048] However, it is also possible that, depending on an area of the
meshed region, the number and dimension of a pore aggregate state or an
area formed by the aggregate state, such selection can be made that the
region concerned is made lower in strength than other regions free of the
above state and equal in strength to a human bone.

[0049] Where irradiation dose per unit area or irradiation time is changed
in the basic configuration (1) and the embodiments shown in FIGS. 3(a)
and (b), in most cases, it is changed by such an embodiment that a
CAD/CAM system 3 shown in FIG. 5 is adopted, a CAD system 31 is used to
set image data corresponding to a shape of the artificial bone 1, and the
CAD system 31 or a CAM system 32 is used to set irradiation dose per unit
area or irradiation time of electromagnetic waves or electron beams 7 at
individual regions of the artificial bone 1.

[0050] In the embodiment adopting the CAD/CAM system 3, where
electromagnetic waves or electron beams 7 are changed at each of
predetermined regions based on the set irradiation dose per unit area or
the set irradiation time of the electromagnetic waves or electron beams 7
corresponding to individual regions of the artificial bone 1, the
artificial bone 1 at the predetermined region changes in strength.
Therefore, appropriate moving velocity and/or rotating velocity where
polishing is performed by the rotating tool 6 also change.

[0051] In coping with the above-described situation, an embodiment is
preferably adopted that in accordance with irradiation dose per unit area
or irradiation time of electromagnetic waves or electron beams 7, the CAD
system 31 or the CAM system 32 is used to set the moving velocity and/or
rotating velocity of the rotating tool 6 as well.

[0052] In general, where a spot diameter to be irradiated with
electromagnetic waves or electron beams 7 is set less than 100 μm, not
only the ends 11 and their vicinities but also other regions can be
molded accurately and finely.

[0054] Hereinafter, an explanation will be made by referring to an
example.

EXAMPLE

[0055] In the example, powder 2 which is metal biomaterial powder or
substantially composed of the metal biomaterial powder is adopted as
laminated powder 2 at both ends and their vicinities configuring a joined
part.

[0056] In this example, only metal biomaterial powder or powder
substantially composed of the metal biomaterial powder is used at both
ends and their vicinities, thus making it possible to maintain necessary
strength and also cope with friction and fatigue at the joined part, in
addition to the basic configuration (1).

[0057] Where powder 2 other than the powder described above in the example
is adopted at regions other than the both ends 11 and their vicinities,
the powder 2 is switched to the above-described powder to effect
laminating at a stage where the both ends 11 and their vicinities are
subjected to irradiation. Therefore, in the example, two or more nozzles
are preferably used for spraying the powder 2.

EFFECTS OF THE INVENTION

[0058] Based on the previously described basic configurations (1), (2),
(3) and (4), in the case of the artificial bone of the present invention,
it is possible to accurately mold the artificial bone at the ends and
their vicinities configuring a joined part to a human bone with necessary
strength and to exert functions fundamentally required for an artificial
bone.

[0059] The present invention is widely applicable in producing and using
artificial bones.